These studies are directed toward evaluation of the prognostic power of the electrocardiogram when analyzed by advanced computer methodology, and the predictive accuracy of diagnostic criteria when implemented in ECG computer programs. Digital signal processing of the electrocardiogram is a problem area requiring considerable engineering and computer science expertise as well as knowledge about its clinical relevance. the use of well documented populations and multivariate statistical techniques in designing new criteria are also subjects under investigation. Studies have been pursued in collaboration with NHLBI, the Framingham Heart Study, and the European consortium (CSE).